The invention relates to a three-ring needle bearing having two concentric, radially separated arrays of bearing needles.
A particular application for the three-ring bearing is to convert concentric rotation of a shaft into eccentric orbital motion of a mounting. This has particular application for use in a pump but is not limited for use only in a pump. The eccentric motion is produced by an eccentric ring between the two concentric arrays of needles.
Three-ring bearings are known from DE 196 32 167. However, that bearing unit is highly complex. It is necessary to incorporate a groove in the hole or bore in the eccentric center ring in order to fix the inner needle array axially in the groove.
Furthermore, the axial guides for the needle arrays may present problems. For example, the projection/groove connection between the cage for the inner needle array and the eccentric center ring may be worn. As a result, the inner array cage makes sliding contact on the sickle-shaped free space of the eccentrically designed molding on the outer race. In addition, the outer ring together with the outer needle array are secured axially only in one direction, so that the three-ring bearing can come apart during its installation.
Furthermore, the eccentric center ring must be provided with a threaded section for securing the torque transmission sleeve. The latter sleeve, as well as the mating piece, are equipped with a complex multiple tooth system, which does not axially fix the three-ring bearing with the electric motor.